Today, for efficiency reasons, the nacelles of wind turbines are placed on top of high towers. In general high towers mean a higher wind speed and thus higher energy production. Access to the nacelle is normally given via the tower, wherein conventional wind turbine towers comprise ladders (in one or several flights) from the bottom of the tower to the nacelle. Since climbing ladders that high is both fatiguing and dangerous, many modern wind turbines have in addition to the ladder a service-lift installed to the tower.
Depending on the space in the bottom of the tower, the service-lift ideally has its lowest position on the bottom platform. The service-lift then travels all the way up to the top of the tower. The highest position of the service-lift is determined by the space in the tower top, but also by the height of the service-lift and its suspension beam. To reach the nacelle from the highest landing platform of the service-lift a climbing of further ladders is required. In conventional wind turbines, there may be one ladder flight to the yaw platform and other ladder flights from the yaw platform to the nacelle.
Climbing these ladders is still fatiguing and dangerous but also inconvenient especially if tools or other equipment must be brought to the nacelle. Today, the lifting of the service-lift ends at the top region of the tower so that further ladders are necessary to reach the nacelle.